Sensor array for detecting the movement of a positioning element moved back and forth using an actuator

ABSTRACT

The invention relates to a sensor array for detecting travel of a movable member, especially a positioning element that is movable using an actuator. Said sensor array comprises a stationary coil arrangement ( 18 ) that is provided with an active coil ( 18.1 ) and at least one passive coil ( 26.1, 26.2 ) located a distance therefrom. The coil arrangement ( 18 ) is connected to a power supply unit ( 30 ) and a signal-detecting device ( 29 ). The inventive sensor array further comprises an axially movable rod-shaped sensor part ( 17 ) that is made of a preferably magnetizable material, is connected to the positioning element which is movable fore and aft in an axial direction, and is provided with at least one short circuit element ( 23, 23.0 ). Said at least one short circuit element ( 23, 23.0 ) is made of an electrically conducting material having low ohmic resistance, is delimited by a final edge ( 23.1, 23.2 ) in the longitudinal direction, respectively, and has a dimension in the direction of movement, which is calculated such that one final edge ( 23.1, 23.2, 23.3 ) of the at least one short circuit element ( 23 ) is enclosed by the active coil ( 18.1 ) in at least one final position (I, II) defined by the predefined length of stroke (h) while another final edge ( 23.1, 23.2, 23.3 ) of the at least one short circuit element ( 23, 23.0 ) is at least partly embraced by one of the at least one passive coils ( 26.1, 26.2 ).

BACKGROUND OF THE INVENTION

In an actuator for moving a positioning element back and forth,particularly an electromagnetic actuator, the movement of the actuatorarmature is typically identical to the movement of the positioningelement to be actuated, such that it is possible to measure the armaturemovement and consequently the movement of the positioning element in theregion of the actuator.

In an electromagnetic actuator with two spaced-apart electromagnets, thepole faces of which point toward one another and between which anarmature is guided such that it can be moved back and forth against theforce of return springs when the electromagnets are alternately suppliedwith a current, a measurement of the current and/or voltage at therespective attracting magnet and during release of the restrainingmagnet makes it possible to draw conclusions about the armature movementthat can subsequently be used for control purposes if the signals areprocessed appropriately.

An electromagnetic actuator of this type is used, for example, as afully variable valve drive for actuating a gas exchange valve of areciprocating internal combustion engine. In view of stricterrequirements regarding control accuracy, particularly with respect toinfluencing the impact velocity of the armature on the pole face of therespective attracting magnet and therefore also the touch-down speed ofthe gas exchange valve on the valve seat, a measurement of movementsderived from the current and voltage curves at the coils of theelectromagnets no longer appears sufficient because the signals obtainedtherefrom can only be used for the subsequent engine cycle.

Consequently, it is necessary to measure the movement of the armatureand therefore the movement of the positioning element “online” over theentire length of stroke with the aid of a corresponding sensor assembly,such that the power supply of the electromagnets can be influenced byappropriately controlling the actuator, for example, an electromagneticactuator, based on corresponding signals while the actuator moves thepositioning element. This makes it possible to control armature movementin the current engine cycle.

This requirement can only be fulfilled with a displacement sensor with alow error deviation that generates a corresponding signal during theentire stroke, i.e., a sensor that “reproduces” the stroke. Due to therequirements with respect to resolution and accuracy of gas exchangevalves, as well as of injection nozzles and needle valves, associatedwith the relatively short strokes, the sensor assembly needs to belargely protected from interference. This also applies to otherinstances in which the movement of a reciprocating component, forexample, a piston valve or the like, needs to be measured in a highlyaccurate fashion. In this case, the displacement signal being generatedshould be as linear as possible.

A sensor of this type is known, in principle, from DE 101 57 119 A,wherein this sensor requires, however, a relatively long structurallength if accurate measurement signals are to be obtained.

SUMMARY OF THE INVENTION

The invention is based on the objective of developing a sensor assemblythat is equivalent to the previously known sensor assembly, but has asubstantially shorter structural length and generates an essentiallylinear displacement signal.

According to the invention, this objective is attained with a sensorassembly with the characteristics of claim 1, namely a sensor assemblyfor detecting travel of a movable member, particularly a positioningelement that is moved by an actuator, wherein said sensor assemblyfeatures a stationary coil arrangement with an active coil and at leastone passive coil arranged at a distance therefrom, wherein said coilarrangement is connected to a power supply unit and a signal acquisitiondevice, wherein the sensor assembly also features an axially movablerod-shaped sensor part that is preferably manufactured from amagnetizable material and is connected to a positioning element that canbe moved axially back and forth, wherein said rod-shaped sensor part isprovided with at least one short-circuit element that is manufacturedfrom an electrically conductive material with a low ohmic resistance andis respectively delimited by a final edge in the longitudinal direction,and wherein said short-circuit element has a dimension relative to thedirection such of movement that one final edge of the at least oneshort-circuit element is enclosed by the active coil and another finaledge of the at least one short-circuit element is at least partiallyencompassed by one of the at least one passive coils in at least one ofthe final positions I, II defined by the given length of stroke h.

The signal generation described in greater detail below is respectivelyachieved by means of a field variation in at least two coils that isrealized by changing the length of penetration of at least oneshort-circuit element, arranged on the rod-shaped sensor part, into theactive coil, wherein this length of penetration changes with the stroke.The particular advantage of the inventive solution can be seen in thatthe end region of the at least one short-circuit element is stillcovered by one of the two coils when the final position defined by thegiven length of stroke is reached. The otherwise passive second coil isthen activated in this region. The “geometry” of the active coil and theat least one passive coil, i.e., their length, their distance from oneanother and the length of the short-circuit element, is chosen such thata transition from the material of the short-circuit element to thepreferably ferromagnetic material of the rod-shaped sensor part, i.e., afinal edge of the short-circuit element, always penetrates into at leastone of the otherwise passive coils when the material transition definedby the other final edge of the short-circuit element approaches one endof the active coil. This already makes it possible to linearize thegenerated measuring signal. An additional third material transitionbetween the different materials, particularly an additionalshort-circuit element, makes it possible to achieve a linearization ofthe output signal over practically the entire length of the stroke ifthe lengths of the zones of superior electric conductivity that aredefined by the length of the short-circuit elements, as well as thedistance between the two short-circuit elements and the thus-definedlength of the zone of ferromagnetic material, are adapted appropriatelywith respect to the length of the coils.

It is expedient if the length of the active coil is greater than thelength of stroke h to be measured.

In the utilization of electromagnetic actuators for actuating gasexchange valves of a reciprocating internal combustion engine, thisinterconnection can be realized such that one non-actuated and oneactuated gas exchange valve are respectively interconnected in the halfbridge.

One particularly advantageous embodiment of the invention can berealized by arranging two short-circuit elements that are respectivelydelimited by final edges on the rod-shaped sensor part such that theyare spaced apart from one another, and by choosing the distance betweenthe facing ends of the at least two coils as well as the distancebetween the facing final edges of the short-circuit elements such thatone final edge of the at least one short-circuit element is enclosed bythe active coil and another final edge of the at least one short-circuitelement is at least partially encompassed by one of the at least onepassive coils in at least one of the final positions I, II defined bythe given length of stroke h.

The linearity can be additionally improved with technical windingmeasures, for example, by purposefully irregular winding, additionalcompensation winding, or similar measures. When providing two passivecoils, one of which is respectively associated with each end of theactive coils, these passive coils are preferably wound in the samedirection and are connected to one another in series, wherein thesepassive coils are realized in the form of quarter bridge elements andinterconnected with the active coil such that a half bridge is formed.

When the coil arrangement of such a sensor assembly is acted upon by ahigh-frequency alternating current, a high-frequency magnetic field isproduced that acts upon the short-circuit element connected to therod-shaped sensor part and generates eddy currents in the short-circuitelement. The eddy currents in turn produce an opposing magnetic fieldthat counteracts the high-frequency magnetic field, causing thisopposing field in the form of a field displacement. The thus-causedfield variation of the coil manifests itself externally in the form ofan inductance change. If the rod-shaped sensor part with its opposingfield is now moved relative to the coil arrangement, the displacement ofthe sensor part and therefore the displacement of the positioningelement can be measured in a contactless fashion with the aid of acorresponding evaluation circuit based on the inductance chance causedby the field variation. The rod-shaped sensor part preferably consistsof a magnetically permeable or magnetically conductive material. Theshort-circuit element may be realized in the form of a short-circuitring attached to the rod-shaped sensor part. Instead of realizing theshort-circuit element in the form of a short-circuit ring, therod-shaped sensor part of magnetizable material may also be divided andfitted with a rod-shaped intermediate piece of electrically conductivematerial that is fixedly connected thereto.

In order to minimize the effect of external interfering influences, ahousing is provided that largely encloses the coil arrangement andconsists of a magnetically conductive material that, however, has aninferior electric conductivity. This is particularly important if thesensor assembly is directly connected to the actuator and the actuatoris realized in the form of an electromagnetic actuator, namely becausein this case corresponding noise fields are produced by operation of theelectromagnets of the actuator. The coil arrangement is shielded fromthese noise fields by the housing.

Although it would be possible, in principle, to apply the material of aring-shaped short-circuit element to the rod-shaped sensor part in theform of a thin layer by means of vapor deposition, it is expedient forthe short-circuit element in the form of a short-circuit ring to have adistinct wall thickness that preferably lies between 0.1 and 0.5 mm.This can be realized, for example, by machining a groove ofcorresponding depth into the ferromagnetic sensor part, wherein thewidth of the groove corresponds to the length of the respectiveshort-circuit element, and the groove is subsequently electroplated withcopper. A corresponding adaptation of the wall thickness of theshort-circuit element makes it possible to compensate a certaintemperature dependence of the sensor assembly in this case.

This is particularly important in sensor assemblies that are used inconnection with actuators subjected to changing operating temperatures,for example, actuators for actuating gas exchange valves ofreciprocating internal combustion engines. Copper or even aluminum ispreferably used as the material for the short-circuit element, whereinthis results in the specific resistance of the material of theshort-circuit element increasing with the temperature at a givenvoltage, as well as in the intensities of the opposing magnetic fieldand the resulting magnetic field respectively decreasing and increasingaccordingly.

On the other hand, the high-frequency magnetic field of the coilarrangement acting upon the short-circuit element causes a skin-effectfor the electric currents induced in the short-circuit element, i.e.,the eddy currents only flow in a thin layer in the outer wall region ofthe short-circuit ring. Although the specific electric resistance of theshort-circuit ring increases with the temperature, the eddy currentspenetrate somewhat deeper into the material of the short-circuit ring inthis case such that the temperature-related increase in specificelectric resistance is largely compensated by a correspondinglyincreased conductor cross section. At a limited thickness of theshort-circuit element, particularly at a limited wall thickness of theshort-circuit ring, the penetration of the eddy currents is limited asthe temperature increases such that the eddy currents decrease above acertain temperature. The temperature response of the sensor consequentlycan be influenced by the thickness of the short-circuit ring. A suitablechoice of the wall thickness therefore makes it possible to partiallycompensate other temperature-related influences, for example, thetemperature dependence of the permeability of the magnetic core andcladding material.

In another embodiment of the invention, a carrier frequency measuringbridge provided for power supply and signal acquisition purposesfeatures a frequency generator, wherein both coils of the coilarrangement form part of the measuring bridge. In this case, it isexpedient for the frequency generator to generate a high carrierfrequency, for example, on the order of 100 kHz.

BRIEF DESCRIPTION OF THE DRAWING

Other embodiments and advantages of the invention are disclosed in thefollowing description and illustrated in the figures.

The invention is described in greater detail below with reference to theschematic embodiments illustrated in the figures. The figures show:

FIG. 1, an electromagnetic actuator for actuating a gas exchange valve;

FIGS. 2 a), b), c), an enlarged section through a basic variation of asensor assembly with a short-circuit ring and two coils, in differentoperating positions;

FIGS. 3 a), b), c), a modification of the embodiment according to FIG. 2with two short-circuit rings and two coils, in different operatingpositions;

FIG. 4, a circuit arrangement for the embodiment according to FIG. 3;

FIGS. 5 a), b), c), a modification of the embodiment according to FIG. 3with two short-circuit elements and three coils, in different operatingpositions,

FIG. 6, a circuit arrangement for the embodiment according to FIG. 5;and

FIG. 7, a diagram in which the voltage is plotted as a function of thedisplacement, wherein the error deviation is also illustrated in thisfigure.

DETAILED DESCRIPTION OF THE INVENTION

The electromagnetic actuator shown in FIG. 1 is essentially formed bytwo electromagnets 1 and 2 that are enclosed by two housing parts 3.1and 3.27 wherein these two housing parts are spaced apart from oneanother by means of a housing part 3.3 in the form of a spacer, and arepositioned such that their pole faces 4 point toward one another. Anarmature 5 is arranged in the space enclosed by the spacer 3.3 betweenthe two poles faces 4, and is guided in a guide 7 by means of a guidepin 6.1 such that it can be moved back and forth.

The armature 5 is connected to a return spring 8 by means of a guide pin6.2 that is supported on the guide pin 6.1 in the region of the armature5. The lower free end 9 of the guide pin 6.1 is supported on thepositioning element, in this case, for example, on the free end of theshaft 11 of a gas exchange valve that is guided in the schematicallyindicated cylinder head 12 of a reciprocating internal combustionengine. A return spring 13 acts upon the gas exchange valve in theclosing direction (arrow 11.1), wherein the return spring 13 and thereturn spring 8 act in opposite directions such that the armature 5assumes an idle position between the two pole faces 4 of the twoelectromagnets 1 and 2, as shown in FIG. 1, when the electromagnets arein the currentless state.

The housing parts 3.1 and 3.2 of the two electromagnets respectivelyenclose a preferably cuboid yoke member 14, wherein these yoke membersare provided with recesses into which an annularly designed coil 15 isinserted. The respective coils can be alternately supplied with acurrent by means of a control unit, not illustrated in greater detail,for opening and closing the gas exchange valve.

A sensor assembly 16 arranged on the opposite end of the actuatorrelative to the gas exchange valve essentially consists of a rod-shapedsensor part 17, for example, a so-called measuring stilt that forpractical purposes represents an extension of the spring bolt 6.2. Therod-shaped sensor part 17 is enclosed by a coil arrangement 18 that isconnected to a voltage supply and signal acquisition device 19. Duringoperation, the back and forth movement of the rod-shaped sensor part 17in the coil arrangement 18 generates an alternating current or an a.c.voltage that is proportional to the displacement of the sensor part, andtherefore proportional to tile displacement of the armature 5 andtherefore proportional to the displacement of the positioning elementdepending on the circuit arrangement and the design of tile sensor. Adirect tap makes it possible to obtain the armature displacement in theform of a signal, and a speed-proportional signal can be obtained bydifferentiation of the displacement signal.

FIG. 2 schematically shows a basic variation of the sensor assembly. Inthis case, FIG. 2 a shows the design of the sensor while FIG. 2 b andFIG. 2 c show the possible final positions of the rod-shaped sensor partfor the length of stroke h.

According to FIG. 2 a), the sensor assembly essentially consists of therod-shaped sensor part 17 that is encompassed by the coil arrangement 18connected to the voltage supply and evaluation device 19 (FIG. 1) viacorresponding leads 20, 21, 22. In the embodiment shown, the coilarrangement features a long active coil 18.1 and a short passive coil26.1 that are wound on a coil support 27.

The rod-shaped sensor part 17 shown is connected to the positioningelement and is provided with a short-circuit element 23 in the form of aring or sleeve of an electrically conductive material with low ohmicresistance, namely a so-called short-circuit ring. The short-circuitring 23 has two final edges 23.1 and 23.2. Its length relative to thedirection of movement is chosen such that the end region delimited byone final edge, in this case the final edge 23.1, is enclosed by thecentral region MS of the active coil 18.1 while the passive coil 26.1 isfully penetrated by the short-circuit ring in the central position M ofthe stroke h shown in FIG. 2 a).

Once the sensor part 17 reaches the final position I shown in FIG. 2 b),the active coil 18.1 is effectively almost completely penetrated by theshort-circuit ring 23, while the passive coil 26.1 is partiallypenetrated by the adjacent ferromagnetic material. Due to the fact thatthe essentially passive coil 26.1 encloses the final edge 23.2 of theshort-circuit element 23 in the vicinity of the final position I, thecoil 26.1 also becomes active near the final position and contributes tothe linearization of the output signal in the bridge circuit accordingto FIG. 4.

Once the rod-shaped sensor part 17 reaches the final position IIaccording to FIG. 2 c) during the return movement, the final edge 23.1approaches the end of the active coil 18.1 while the short-circuit ring23 is still surrounded by the passive coil 26.1, and the active coil18.1 is effectively almost completely filled with the magneticallyconductive material of the rod-shaped sensor part. A linearization ofthe output signal does not take place in this final position.

With the exception of corresponding through-openings for the rod-shapedsensor part 17, the coil arrangement 18 may be enclosed by the housing24 on all sides. In this case, the housing 24 consists of a materialwith superior magnetic conductivity but inferior electric conductivity,and serves to shield the coil arrangement 18 from the influence ofexternal magnetic fields. The coils can be fixed in the housing 24, forexample, with a pourable sealing compound. This also applies to theembodiments described below.

The short-circuit ring 23 of a material with superior electricconductivity, preferably copper or aluminum, has a thickness that lies,for example, between 0.1 and 0.5 mm. In the embodiment shown, theshort-circuit ring 23 is inserted into a groove 23.3 in the rod-shapedsensor part 17. The rod-shaped sensor part 17 can be directly formed bythe positioning element to be actuated, for example, an injector needleof a fuel injector or the shaft of a gas exchange valve, such that therod-shaped sensor part 17 penetrates the coil arrangement with itsentire length, or by a corresponding bolt of the actuator armature or ameasuring stilt connected thereto.

A sensor assembly of this type operates in accordance with the eddycurrent principle. When a high-frequency alternating current acts on thecoil arrangement 18 such that a high-frequency magnetic field isproduced, electrical potential differences are induced in theshort-circuit ring 23 that are transformed into eddy currents by theshort-circuit. These eddy currents in turn produce an opposing magneticfield that counteracts the high-frequency magnetic field of the coilarrangement 18, causing the opposing field in the form of a fieldvariation. During a movement of the rod-shaped sensor part 17, thedirection and the displacement of the field variation relative to thecoil arrangement manifest themselves externally in the form of a changein inductance that is dependent on the movement of the rod-shaped sensorpart 17. Consequently, this makes it possible to measure the positionand therefore the displacement of the sensor part 17 by means of acorresponding signal.

FIG. 3 shows a preferred embodiment of the sensor assembly in differentoperating positions, wherein this sensor assembly is illustrated inanalogous fashion to that described with reference to FIG. 2. Sinceidentical components are identified by the same reference symbols, werefer to the preceding description in this respect. The coil arrangement18 also features a long active coil 18.1 and a short passive coil 26.1in this embodiment. The difference in comparison with the embodimentaccording to FIG. 2 lies in the fact that the rod-shaped sensor part 17is provided with two short-circuit rings, namely a first short-circuitring 23 and a second short-circuit ring 23.0. The two short-circuitrings 23 and 23.0 are arranged on the rod-shaped sensor part 17 at adistance from one another. The distance between the final edge 23.1 ofthe short-circuit ring 23 and the final edge 23.3 of the short-circuitring 23.0 is once again adapted to the dimensions of the coilarrangement 18. Based on the central position M shown in FIG. 3 a), thefinal edge 23.1 of the short-circuit ring 23 is enclosed by the centralregion MS of the active coil 18.1 while the passive coil 26.1 is stillpenetrated by the ferromagnetic material of the sensor part 17.

Once the sensor part 17 reaches the final position I shown in FIG. 3 b),the active coil 18.1 is effectively almost completely penetrated by theshort-circuit ring 23 while the passive coil 26.1 is still penetrated bythe ferromagnetic material of the sensor part 17 only.

Once the sensor part 17 reaches the final position 11 shown in FIG. 3 c,the active coil 18.1 is effectively almost completely penetrated by theferromagnetic material of the sensor part 17 while the region delimitedby the final edge 23.3 of the second short-circuit ring 23.0 penetratesand therefore activates the thus far passive coil 26.1.

FIG. 4 schematically shows a circuit for the acquisition of measurementsignals, in the form of the carrier frequency measuring bridge, for theembodiments according to FIG. 2 or 3. The coil 18.1 and the coil 26.1 ofthe coil arrangement 18 of the sensor assembly are interconnected withtwo additional impedances, for example, coils 18.3 and 18.4, such that acarrier frequency measuring bridge 29 is formed. The measuring bridge 29is supplied with a high-frequency alternating current by means of afrequency generator 30.

A field variation occurs if the respective active rod-shaped sensor part17, with its short-circuit rings 23 and 23.0, is now moved relative tothe coils 18.1 and 26.1 of the bridge 29 in the direction of the finalposition I. This causes a “detuning” of the bridge 29 that can bemeasured with an amplifier 31 and a band-pass filter 32. Astroke-dependent signal can be obtained with the aid of a rectifier 33,which can be realized in a phase-selective fashion, and a low-passfilter 34, wherein the stroke-dependent signal can subsequently beprocessed for control purposes, for example, in order to control the gasexchange valves. The passive coil 26.1 acts as a compensation coil inthis case. If the sensor part 17 is moved in the direction of the finalposition II, the coil 18.1 becomes passive in the final position IIwhile the passive coil 26.1 becomes active, and thus counteracts thenon-linear signal increase.

FIG. 5 shows a variation of the embodiment according to FIG. 3, in whichtwo short passive coils 26.1 and 26.2 are respectively arranged oneither side of a long active coil 18.1. Since the corresponding circuitarrangement according to FIG. 6 essentially corresponds to the circuitshown in FIG. 4, we refer to the description of FIG. 4 in this respect.The two coils 26.1 and 26.2 are connected in series in this case. Theinductance of the active coil 18.1 approximately corresponds to the sumof those of both passive coils 26.1 and 26.2. The two passive coils 26.1and 26.2 are electrically connected in series and form one-quarter ofthe carrier frequency bridge 29.

The distance between the two short-circuit rings 23 and 23.0, as well asthe length of both short-circuit rings 23 and 23.0 relative to the coilarrangement shown, are chosen such that in the central position of thefinal edge 23.1 of the short-circuit ring 23, said edge lies in thecentral region MS of the coil 18.1 and coil 26.1 still completelyencloses the short-circuit ring 23 while the coil 26.2 is fullypenetrated by the ferromagnetic material of the sensor part 17, and theshort-circuit ring 23.0 therefore lies outside the area of influence ofcoil 26.2.

According to FIG. 5 b), the short-circuit ring 23 is effectively almostcompletely enclosed by the coil 18.1 in the final position I while thepassive coil 26.1 is partially penetrated by the adjacent ferromagneticmaterial of the sensor part 17 and the passive coil 26.2 is completelypenetrated.

If the sensor part 17 is displaced into the final position II shown inFIG. 5 c), the final edge 23.3 of the short-circuit ring 23.0 reachesthe region in which it is overlapped by the coil 26.1 while theshort-circuit ring 23 overlaps the area of influence of the coil 26.2.The coil 18.1 is effectively almost completely penetrated by theferromagnetic material of the sensor part 17 in this position.

FIG. 7 shows a diagram in which the voltage V is plotted as a functionof the length of stroke h. This figure also shows the resultingmeasurement errors of different systems in relation to the actualdisplacement.

The line V shows the voltage for a stroke of 8 mm. The broken line IRindicates the absolute measurement error for the embodiment according toFIG. 2 with only one short-circuit ring, in millimeters, while thecontinuous line 2R indicates the error deviation for an embodimentaccording to FIG. 5 with two short-circuit rings, a long active coil18.1 and two short passive coils 26.1 and 26.2. According to thisdiagram, the embodiment according to FIG. 5 results in a significantlyimproved linearity of the measuring signal.

1. Sensor arrangement for the collection of stroke data for a movableelement, in particular by an actuator movable through a control member,said arrangement comprising an active coil (18.1) located a distancefrom at least one passive coil (26.1, 26.2) exhibiting coil arrangement(18); having a current supply (30); and a signal collector (29); and anaxially movable rod-shaped sensor part (17) preferably formed from amagnetizable material, said rod-shaped sensor part axially moving backand forth the movable control member in connection therewith between endpositions and having a long axis ending in a trailing edge (23.1, 23.2);wherein a short-circuit element (23, 23.0) is provided that is formedfrom an electrical-conductive material having a small Ohmic resistance,said short-circuit element extending so as to limit the direction ofmotion as defined by at least one of the given stroke-height (h) definedend position (I, II), and a trailing edge (23.1, 23.2, 23.3) wherein atleast a short-circuit element (23) is enclosed by the active coil (18.1)and another trailing edge (23.1, 23.2, 23.3) of at least a short-circuitelement (23, 23.0) is at least partly covered by at least one passivecoil (26.1, 26.2) and the passive coil is activated upon reaching one ofthe end positions of a linear movement producing measuring signal. 2.The sensor arrangement according to claim 1, characterized by thetrailing edge of the short-circuit element interfaces with a switch atan end of the active coil, wherein another end of the short-circuitelement is the passive coil.
 3. The sensor arrangement of claim 1,characterized by the rod shaped sensor part (17) having two marks ineach case by trailing edges (23.1, 23.2) to limit the short circuit (23,23.0) distance to between the two marks and such that the distance ofeach of two course-turned ends is limited to between two coils (18.1,26.1) and the distance of the each other course-turned trailing edges(23.1, 23.2) of short-circuit elements (23, 23.0) is also limited to thegiven stroke-height (h) defined end position (I, II) of the sensorelement (17) one of the trailing edges (23.1, 23.2, 23.3) of theshort-circuit elements (23, 23.0) is enclosed by the active coil (18.1)and the other trailing edge (23.1, 23.2, 23.3) of at least theshort-circuit element (23, 23.0) is at least partly covered by the atleast one passive coil (26.1, 26.2).
 4. The sensor arrangement accordingto claim 1, characterized by the active coil (18.1) having a longerlength than the passive coil (26.1, 26.2) in the direction of the motionof the sensor part of (17).
 5. The sensor arrangement of claim 1,characterized by an arrangement of one passive coil (26.1, 26.2)positioned beneath the active coil (18.1) and the distance of the eachother course-turned trailing edges (23.1, 23.2) of the two short-circuitelements (23, 23.0) is limited the distance extending between the twoshort-circuit elements (23, 23.0) to the given stroke-height (h) definedend position (I, II) of the trailing one of the short-circuit elements(23, 23.0) and is enclosed by the active coil (18.1) and one of the twoshort-circuit element (23, 23.0) is at least partly covered by the atleast one passive coil (26.1, 26.2).
 6. The sensor arrangement accordingto claim 5, characterized by, the two passive coils (26.1, 26.2) beingelectrically connected one behind the other to form a quarter frequencycarrier bridge (29).
 7. The sensor arrangement according to claim 1,characterized by, at least the active coil (18.1) is purposefully massunbalance wound.
 8. The sensor arrangement according to claim 1,characterized by, the active coil (18.1) has an active coil length andthe short-circuit element (23) has a short-circuit element length thatis longer than the length of the active coil (18.1).
 9. The sensorarrangement according to claim 1, characterized by, the active coil(18.1) has a length that is longer than a measurable for thestroke-height (h).
 10. The sensor arrangement according to claim 1,characterized by, an inductivity of the active coil (18.1) is the sum ofthe inductivities of the passive coils (26.1, 26.2).
 11. The sensorarrangement according to claim 1, characterized by, the short-circuitelements (23, 23.0) have a wall thickness that at least in partcompensates for a temperature change influence on the sensorarrangement.
 12. The sensor arrangement according to claim 1,characterized by the active coil (18.1) and the least a passive coils(26.1, 26.2) are connected in a half bridge and effect range of thesensor part of (17), such that the active coil receives thestroke-height (h) limiting end position (I, II).
 13. The sensorarrangement according to claim 1, characterized by, the current supplyand signal collector form a carry frequency measuring bridge (29),whereby the active coil (18.1) and the passive coils (26.1, 26.2) form apart of the measuring bridge (29) for the coil arrangement (18).
 14. Aprocedure for the collection stroke data for a movable element, inparticular a control member movable by an actuator, wherein by a fieldvariable is established between two coils bounding stroke length, ashort-circuit element on a rod-shaped sensor part in an active coil atthe part moves between the two coils and induces a signal generation,the short-circuit element is bounded by a given stroke-height definedend position such that the short-circuit element has a range within thetwo coils and a trailing edge of the short-circuit element travels intoa passive coil, and when another trailing edge of a short-circuitelement crosses an end of the active coil a linear measuring signal isproduced.
 15. The procedure according to claim 14, characterized by onthe rod-shaped sensor part is bound by two short-circuit elementtrailing edges that define the stroke-height wherein one of the trailingedges of a short-circuit element is enclosed by the active coil and afurther edge one of the two short-circuit elements is at least partlycovered by the passive coil.